Application of Calcium-rich Clay Mineral Under Nonwoven Fabric Mats and Sand Armor as Cap Layer for Interrupting N and P Release from River Sediments

This work investigates the applicability of thermally treated calcium-rich clay minerals (CRCMs), such as sepiolite (SPL), attapulgite (ATT), and dolomite (DLM) to hinder the nitrogen (N) and phosphorus (P) release from river sediments. A non-woven fabric mat (NWFM) or a sand layer were also capped as armor layers, i.e., placed over CRCMs to investigate the capping impact on the N/P release. The capping efficiency was evaluated in a cylindrical reactor, consisting of CRCMs, armor layers, sediments, and sampled water. We monitored N/P concentrations, dissolved oxygen (DO), oxidation reduction potential, pH, and electric conductivity in overlying water over 70 days. The DO concentrations in the uncapped and capped conditions were preserved for 30 days and 70 days (until the end of experiment duration), respectively. ATT showed higher efficiency for NH4-N and T-N than the other two materials, and the capping efficiency of NH4-N was measured as 96.4%, 93.7%, and 61.6% when capped with 2 cm sand layer, 1 cm sand layer, and NWFM layer, respectively. DLM showed a superior rejection capability of PO4-P to ATT and SPL, reported as 97.2% when capped with 2 cm sand armor. The content of weakly adsorbed-P was lower in the uncapped condition than in the capping condition. It can be concluded that ATT and DLM can be used as capping agents to deactivate N and P, respectively, to reduce water contamination from sediments of the eutrophic river.

Влияние гранулометрического состава песка на глубину проникновения дизельного топлива

Deployment of tanks for temporary storage of fuel on sand layer (a sand blanket) is an effective method to protect the soil from process-related spills. Asessment of the required thickness of the sand layer is important in practice, as it determines the layer’s protective properties when oil droplets fall on the surface. This paper investigates the dependences of the speed and depth of ingress of DT-Z-K5 diesel fuel on the grain size composition of the sand used as a protective layer. Substantiation has been given for the approach to the evaluation of the kinetics and to the depth of ingress of petroleum products into the sand, such approach being based upon the probabilistic movement of the fluid flow boundaries in the protective layer. It is proposed to describe the ingress of fuel into the sand layer in the coordinate system of the square root of the process time. Based on the results of the study, there have been established the dependences of the speed and depth of ingress of DT-Z-K5 fuel into the protective layer on the sand grain size and on the quantity of petroleum product leaked on the surface. It has been established that to create a protective layer preventing the ingress of fuel into the soil in the event of process-related leaks in temporary fuel storage tanks, it is optimal to use sand with 0.8 mm grain. Размещение резервуаров для временного хранения горючего на слое песка (песчаной подушке) является эффективным способом защиты грунта от технологических проливов. Практическое значение имеет оценка необходимой толщины песчаного слоя, которая определяет его защитные свойства при попадании на поверхность капель нефтепродукта. В настоящей работе исследованы зависимости скорости и глубины проникновения дизельного топлива ДТ-З-К5 от гранулометрического состава частиц песка, используемого в качестве защитного слоя. Обоснован подход к оценке кинетики и глубины проникновения нефтепродукта в песок, основу которого составляет вероятностное движение границ потока жидкости в защитном слое. Предложено описывать проникновение топлива в слой песка в системе координат корня квадратного из времени процесса. По результатам исследования установлены зависимости скорости и глубины проникновения ДТ-З-К5 в защитный слой от размера частиц песка и количества вносимого на поверхность нефтепродукта. Определено, что для создания защитного слоя, исключающего проникновение топлива в почву при возникновении технологических протечек резервуаров временного хранения горючего, оптимально использовать песок с размером частиц от 0,8 мм. Предложенный подход по получению зависимостей глубины проникновения топлива от условного времени можно использовать для оценки распределения топлива в слоях песка с различными размерами частиц.

Permeable reactive barrier of waste sludge from wine processing utilized to block a metallic mixture plume in a simulated aquifer

Heavy metal contamination in underground water commonly occurs in industrial areas in Taiwan. Wine-processing waste sludge (WPWS) can adsorb and remove several toxic metals from aqueous solutions. In this study, WPWS particles were used to construct a permeable reactive barrier (PRB) for the remediation of a contaminant plume comprising HCrO4−, Cu2+, Zn2+, Ni2+, Cd2+, and AsO43− in a simulated aquifer. This PRB effectively prevented the dispersals of Cu2+, Zn2+, and HCrO4−, and their concentrations in the pore water behind the barrier declined below the control standard levels. However, the PRB failed to prevent the diffusion of Ni2+, Cd2+, and AsO43−, and their concentrations were occasionally higher than the control standard levels. However, 18% to 45% of As, 84% to 93% of Cd, and 16% to 77% of Ni were removed by the barrier. Ni ions showed less adsorption on the fine sand layer because of the layer's ineffectiveness in multiple competitive adsorptions. Therefore, the ions infiltrated the barrier at a high concentration, which increased the loading for the barrier blocking. The blocking efficiency was related to the degree of adsorption of heavy metals in the sand layer and the results of their competitive adsorption.

Bearing capacity of rectangular footing on layered sand under inclined loading

Purpose: The study presents the numerical study to investigate the bearing capacity of the rectangular footing on layered sand (dense over loose) using ABAQUS software. Design/methodology/approach: Finite element analysis was used in this study to investigate the bearing capacity of the rectangular footing on layered sand and subjected to inclined load. The layered sand was having an upper layer of dense sand of varied thickness (0.25 W to 2.0 W) and lower layer was considered as loose sand of infinite thickness. The various parameters varied were friction angle of the upper dense (41° to 46°) and lower loose (31° to 36°) layer of sand and load inclination (0° to 45°), where W is the width of the rectangular footing. Findings: As the thickness ratio increased from 0.00 to 2.00, the bearing capacity increased with each load inclination. The highest and lowest bearing capacity was observed at a thickness ratio of 2.00 and 0.00 respectively. The bearing capacity decreased as the load inclination increased from 0° to 45°. The displacement contour shifted toward the centre of the footing and back toward the application of the load as the thickness ratio increased from 0.25 to 1.25 and 1.50 to 2.00, respectively. When the load inclination was increased from 0° to 30°, the bearing capacity was reduced by 54.12 % to 86.96%, and when the load inclination was 45°, the bearing capacity was reduced by 80.95 % to 95.39 %. The results of dimensionless bearing capacity compare favorably with literature with an average deviation of 13.84 %. As the load inclination was changed from 0° to 45°, the displacement contours and failure pattern shifted in the direction of load application, and the depth of influence of the displacement contours and failure pattern below the footing decreased, with the highest and lowest influence observed along the depth corresponding to 0° and 45°, respectively. The vertical settlement underneath the footing decreased as the load inclination increased, and at 45°, the vertical settlement was at its lowest. As the load inclination increased from 0° to 45°, the minimum and maximum extent of influence in the depth of the upper dense sand layer decreased, with the least and highest extent of influence in the range of 0.50 to 0.50 and 1.75 to 2.00 times the width of the rectangular footing, respectively, corresponding to a load inclination of 45° and 0° Research limitations/implications: The results presented in this paper were based on the numerical study conducted on rectangular footing having length to width ratio of 1.5 and subjected to inclined load. However, further validation of the results presented in this paper, is recommended using experimental study conducted on similar size of rectangular footing. engineers designing rectangular footings subjected to inclined load and resting on layered (dense over loose) sand. Originality/value: No numerical study of the bearing capacity of the rectangular footing under inclined loading, especially on layered soil (dense sand over loose sand) as well as the effect of the thickness ratio and depth of the upper sand layer on displacement contours and failure pattern, has been published. Hence, an attempt was made in this article to investigate the same.

New Formula for the Identification of Liquefaction Based on the Investigation of the Songyuan Site

Based on the 5.7-magnitude earthquake that stroke Songyuan (China) and 172 groups of liquefaction data collected in mainland China, the hyperbolic liquefaction discriminant formula originally proposed by Sun Rui was revised, and a new formula for the liquefaction of sand was put forward. Groups of data derived from the Bachu earthquake in Xinjiang and an earthquake that occurred in New Zealand (47 and 195 groups, respectively) were used to carry out a back-judgment test, then, the results were compared with those of the existing standard method. Overall, the results showed that the new formula for hyperbolic liquefaction discrimination compensates for the conservative liquefaction discrimination of the older formula; moreover, it has a good applicability to different intensities, groundwater levels, and the deep sand layer of the Songyuan site, reflected by a more balanced success rate. Therefore, combining the existing liquefaction discrimination methods and the research results of discrimination, it is necessary to establish a suitable regional identification method through the continuous accumulation of liquefaction data and expanding database.